Generally, an air purifier suctions polluted air from an indoor space, filters dust, odor particles, and the like contained in the air using a filter to purify the air, and discharges the purified air to the outside of the air purifier through an outlet thereof.
Further, the air purifier includes various filters installed to purify introduced air including various sizes of dust particles, odor particles, harmful gas, and the like.
Meanwhile, when dust is accumulated on the filter of the air purifier, dust collection performance is degraded, and thus air purification performance is also degraded.
To prevent the degradation of air purification, a method in which the air purifier notifies of a filter replacement time on the basis of an accumulated use time or a user directly checks a state of a filter and replaces the filter is used.
However, the above-described filter replacement method has problems. When the air purifier is located in a relatively less polluted place, the air purifier notifies of a replacement of a filter even though the filter replacement time has not arrived. When the air purifier is located in a relatively more polluted place, the replacement notification of the filter is delayed even through the filter replacement time has elapsed.
Further, when a user directly and visually checks a state of a filter and replaces the filter, it is hard for the user to accurately determine a time at which the filter should be replaced even though dust is accumulated on the filter.
Therefore, a technology of more accurately providing a filter replacement time of an air purifier is required.